1967 Super Bass Build

[Danhalen]

Hi DanHalen!

Co-incidentally, I'm in the middle of a similar build that I put on hold almost a decade . Nothing much to offer other than friendly chit chat Late '67 build, Marstran xformers (1202-132/ 1203-80). 3H choke

I'm starting out filtering 100/100 mains, 32/32 screens, 32 PI, and 32+32 preamp. Shared cathode, single rectifier, 470k mix resistors, 27k on 16ohm NFB. Modern CF resistors except the long ones are CC, mustard signal caps. The only thing I'm humming and hawing about is the 2@ 1k5 or 4@ 5.6k grid stoppers (stupid, I know...) and I'm gonna start out by using the two voltage droppers (8.2k + 10K). I decided to use modern el34's, let's see how long I can control myself . My last build was 10 years ago (JTM45) which I just love, but I've always been drawn to 100 watt amps so I went this route. I use an attenuator.

Oh yeah, I put a pull/push knob o the bright channel with a 5000pf cap.

The only thing is the xformer wait times are quite long - at least 5 weeks.

Hi Kats. Very cool! That is a funny coincidence. Your build really is very close to what I am thinking about doing! Also, when I built my 50 watter, also about a decade ago, I had a hard time deciding whether to build it or a JTM 45. I would love to have a JTM 45 or 50 as well... I love the singing, vocal quality to the midrange that they have and the bit of chime in the high end, not to mention the amazing sag in the attack.

Also just for conversation: my 50 watter was my first amp build, so I probably won't be posting any gut shots! It sounds great though. It is a basically stock 1986 specs, Metroamp kit with George's transformers. No bright cap, nfb 27k on the speaker jack. I thought I preferred it through 8ohms (slightly lower nfb), but lately I have actually been preferring the slightly higher feedback at 16ohms. Then again, a lot of that tonal bliss has to do with the amazing sounding 4x12 cabinet that I recently got... I tried so many variations with the amp, lead spec, bass spec, various halfway combinations, every different bright cap, cathode bypass caps etc. In the end I settled on bass spec and the only 'mod' it has is lower than stock filtering on the PI and Screens (I swapped out the 50/50 can for a 32/32 can). I have it on the bench now to fix a worn input jack (it has had a lot of use!). I think I might mess around with the lowering the mains filtering, just for the heck of it. It does sound great as is though. I am fortunate to have a recording/rehearsal space where volume is not an issue. I generally do not play it with an attenuator there. It has been a while since I have gigged with this amp, but when I did I always brought an attenuator but did not always use it. Depended on the venue of course and I was not running the thing on 10 either... Oh and at the time I was using a 4x12 with Celestion heritage 20w speakers, which would knock off a bit of volume (I'm digging G12h speakers more these days). I used to always say that I would post a clip of it and I am not sure if I ever did! I should really do that just for kicks.

Your amp build is exciting. You should post a clip when it is done! Over the last weekend, I was thinking maybe I would veer more towards 10000 series with my build. Funny how we agonize over the little details and drive ourselves crazy. For you it's the grid stoppers, for me it is the dual vs single rectifier. I guess maybe we enjoy fussing over that stuff, who knows. In the end, either way would probably work out fine (speaking for both of our situations there...).

[neikeel]

...my latest 45/100 (Hendrix/Dickinson spec) is very punchy and suitably cranked has plenty of gain for classic/heavy rock (not metal unless goosed with a pedal).

I can imagine myself loving that set up. Have you tried modern KT66's? I only have experience with GEC's and wouldn't want to waste money on a quad that would a) not last, b) not sound that great.

Yes the Gold Lions sound very similar, service life is probably shorter tho'.

[kats]

That’s good to know Neil, perhaps I’ll buy a pair for jamming and save the NOS stuff for when it counts (although the word “when” is optimistic LOL).

Re: Grid stoppers. So today I forced myself to stick with my original intention and not get all nostalgic if it’s not a step forward. But damn, those 5.6k’s standing up in the air like that on each OP tube looks so flakey...

[kats]

Oh and at the time I was using a 4x12 with Celestion heritage 20w speakers, which would knock off a bit of volume (I'm digging G12h speakers more these days). I used to always say that I would post a clip of it and I am not sure if I ever did! I should really do that just for kicks

Funny, I have the heritage g12m in a cab from back then and have been sussing out getting another and loading it with g12h (55 or 75). Kinda wary getting the Celestions as you really need to kick the crap out of them for break in and have been considering Scumbacks. We’ll see...

But for sure, clips would be great - I’ll do the same. Ps Neil, do you ever post clips of your amps? If so, I’d love to hear them.

[neikeel]

But for sure, clips would be great - I’ll do the same. Ps Neil, do you ever post clips of your amps? If so, I’d love to hear them.

I am quite shy about recording stuff - very picky and would not want to post dodgy clips that does not give the gear justice, I play out with our band and don't worry about that any more (used to be quite nervous even after hundreds of gigs) but clips can be quite telling! I have run out of excuses as I have a decent basic mic (SM57) and two channel interface and a Motherload elemental to blend the two, except my son has nabbed them for his rig!

[kats]

Interesting topic. I know quite a bit about engineering records, recording studios etc. and recording distorted guitars is quite tricky compared to other instruments in the "rock" genre. In most cases we can achieve a sense of "hyper-reality" - drums, vocals etc., but do recorded distorted guitars ever really sound better than they did in the room?

I think the best guitar recordings are the ones someone else did, 'cause you never got to hear how good it really sounded . I'm being a little facetious, but it is a bit true. A long winded way to say that if you ever were 100% satisfied with your guitar recording, there is something wrong with you so let it go. It is very difficult to record something that relies on high volumes pushing lots of air through a cabinet of 12" speakers to translate at low volume on (at best) 4" monitor speakers. It's a lot better if you listen to playback loudly, but mostly it is not practical.

Now I'm rambling, maybe you guys share the interest. Personally, I'm not a fan of SM57's on cabs - I know many do it, but I feel it's like giving up on life. The simplest, almost funny, is nothing more than a Sennheiser MD409 stuffed right in the middle of the speaker. Damn things are getting expensive now if they are in good repair. The sound/tone is "right there". You just have to figure out how to translate the "feel" of it in the mix.

Check this chain out - I used to own (I am no longer in the game) Helios Type69 channel strips out of the original Island Basing Street Studios Helios desk (think Zeppelin, Free, and Hendrix juju flowing through those circuits ), into a Studer A827 with a custom 16 track 2" head stack slamming Amperex 456 (I can smell it now ). Normally mic'd the amps with vintage U87 p48's (the newer U87's are higher output, lower headroom and distort 6dB sooner than the older ones). It sounded good.

[Danhalen]

Interesting clips.
I would have thought the 71 SL would be much brighter - mine was (but not sure where he EQ'd it)
When maxed out it is surprising how the SL and SB sound relatively similar
Of course the 67 SB is the same as a SL apart from a bright cap on the Vol 1 pot.

I was listening to those clips again. Man oh man that amp sounds good to me. Pretty cool that he has gut shots in there too. To my only sort of experienced eye, the amp looks like it is stock dual rectifier circuit, except PI filtering raised to 32uf? I think all of the filter caps look like 32uf, including the one that has been replaced. I can't make out the mixer resistors, but since it is a 'JMP' panel amp, likely 470k. 119 OT. When he opens up with the Strat and when he plays the Les Paul there is a lot of bass (doesn't sound like it is on zero I don't think). Any other mods or weird stuff going on do you guys think?

What a great sounding amp, the balance of tightness/looseness is so nice and when he plays high notes on the Strat the amp smooths out the spikey transients (I have watched a few of his other clips and that is a great sounding strat, so that helps too). Definitely sounds like it has a foot in JTM land and another in JMP land.

[Danhalen]

I have a couple practical questions about the black flag JTM 100:

-Is it the power board the size as the JTM 45/100 power board? Could I use a Valvestorm JTM 45/100 power board, order it without turrets and install my own? In pictures it looks like the board is the same size I think...
-Just out of curiosity, those of you who built an amp with the 1202-119 output transformer, what did you do about the impedance switch? Did you put a little shim in there to block off the 4ohm position on the switch? Paint over the 4 with a sharpie?

[neikeel]

The board is the same size as the JTM45/100.

I made mine with the 1202-132 which has 4, 8 and 16ohm taps.

My original '67 blockend 45/100 had -119OT with 8, 16 and 100v taps and selector (even though it was always a lead spec amp

[kats]

I had emailed valvestorm with the exact same question. When I didn't get a reply, a quick internet search found multiple resources for perforated turret boards and turrets in the US. I believe tubesandmore.com were one of them. Perhaps Neil remembers the dimensions?

If I were to do mine again, I would have made my own board.

[Danhalen]

Thanks for the info guys, if the board is the same size I am sure that Valvestorm could just sell me one with no turrets. I like the idea of getting the chassis and boards from the same source, so that hopefully they'll go together more easily and I can get on with the more fun parts of the build

I am leaning towards forgetting the switchable mains for now and just building a black flag, pretty close to stock and taking it from there.

I just thought of one other little question that I could not find searching around: When building a 10000 or 12000 series on the typical steel chassis, I believe that there is one socket hole that needs to be covered. For a black flag build, there would be two because there would be no PI filter cap on top of the chassis right? Does the same socket cover thingy fit, or did you guys who have built one of these have to fab something up?

[kats]

The socket cover valvestorm sells works for both holes.

[Danhalen]

I like the following:
22+22uf preamp
32uf PI
16uf screens
33uf/50uf mains
Switchable mains works well for me. The rectifier or PT doesn't matter too much if it has the right vintage specs. 33uf is great for Cream, Free and blues. 50uf is much better for ac/dc

Thanks Kats.

There is a lot of good information in this thread!

Roe, I am curious why you prefer the slightly lower preamp filtering in this amp? Does it soften the transients, or make high notes a bit smoother? Or is it more of a feel thing?

[Danhalen]

I am almost ready to get started ordering my parts. Valvestorm can hook me up for the power board for the dual rectifier setup or a blank board and turrets as well.

I think I will explore tweaking preamp and mains filtering with this build for sure. I love smoothness of the 45/100 and the punchiness of the 10000 series. The black flag seems to sit in the middle and I love the amount of squish I hear in the attack, it's just right. It seems though that the price for that attack is a sort of weird buzzy graininess in the attack. I wonder if I can achieve a similar feel and squish/punch balance with a single rectifier by playing with the preamp and mains filtering a bit. Just thinking out loud here... I think the long term answer is multiple '67 builds, no way around that I guess. Good problem to have...

Neil how many '67's do you have?

[neikeel]

All gone now
I have a 64 JTM45, 65 JTM45, early 69 JMP50, early 45 clone, 50w 2 in 1, 68 BB combo, 18w Trem comb, 18w TMBEF86 and an 18w head, 45/100 JH clone. A few Oranges (30, 50, 100 and a couple of OR120s), Selmer TnB 50 MkII, plus some projects to finish (DR103, JMP50, JMP100) but no 67s left.